1. Field
One embodiment of the invention relates to a video signal control apparatus and a video signal control method for displaying video with controlled display luminance.
2. Description of the Related Art
Self-luminous display panels, such as organic electroluminescence (EL) panels, have a high correlation between the display luminance and the power consumption. In such a display panel, when the average luminance of a video signal is low, the display luminance is controlled to be higher (brighter). When the average luminance of a video signal is high, the display luminance is controlled to be lower (darker). Thus, a balance is achieved between image quality (brightness and contrast) and restriction on the maximum power consumption.
Japanese Patent Publication No. 3592126 discloses a video signal control method, in which the average luminance of a video signal is detected with respect to each frame, and the display luminance is controlled according to the average luminance. More specifically, a correlation between frames of a video signal is detected as a frame correlation. A gain is set according to the frame correlation so that the display luminance changes slower when the frame correlation is high, while it changes faster when the frame correlation is low.
The display luminance control based on the average luminance of a video signal may cause the display luminance of the entire screen to change even when only part of the screen changes, as, for example, when only the foreground moves without change in the background, resulting in unstable video display. Meanwhile, when, for example, the entire screen changes as in a scene change, such control may reduce response to a change in the display luminance.